re: Corsi-Rosenthal Air Filter Box

Other than it working as it is supposed to I cannot really say what differentiates a good one from bad.   Dylos is one brand that I have seen in the past that was always held up as low end professional quality meter but they are pretty expensive and the reviews seemed kind of mixed to me.  I searched for "air quality monitor" to find others.   The meter above with the color display is the same model that the guy in the second video above used.  He seemed to think it worked well so I ordered that one. It has pretty good reviews.   

The other one I found by reading reviews and is made by Temtop who has several other versions including handheld ones.  I chose it because it seems to have decent reviews and selected the version that is WiFi enabled so I can look at the history in an app (on iPhone at least).  I think that you can also export the data for further analysis but have not tried that yet.  Below is a screen shot of the app during the above tests yesterday.  The first hump in the graph is the first test where I stirred up some dust and the filter brought the counts down by the time I checked on it 15 minutes later.  The second hump is where I stirred up the dust mother load and the graph shows that it gradually dropped for the first 15 minutes.  You can see where the PM2.5 count drops dramatically when I switched the air filter back on.    This one does not report PM1 or PM10 levels as the other one does. 

I believe that Temtop also makes a version that you can download the historical data from.   Both of these meters are powered by USB cables and have a battery so that they can operate for a little while without being plugged in.  I considered an Amazon branded monitor that is supposedly Alexa enabled but the reviews were sort of meh and it doesn't have a display so you have to rely on Amazon and Alexa to see what is going on.  A common complaint is that without an Echo Show you cannot see details.